Heat treatment system



Il E

H. E. KOCH ET AL HEAT TREATMENT SYSTEM Filed Deo.

Oct. 25, 1932.

Patented oa. 25,1932

.e conronarlon or WISCONSIN HAROLD E. KOCH, 0F WAUWATOSAQANID MELYILLELOWE, 0F MILWAUKEE, WISCONSIN,

ASSIGNORS T0 HEVI DUTY ELECTRIC COMPANY, 0F MILWAUKEE, 'WISCQNSIIL AHEAT TREATMENT SYSTEM,

appunti-cn mea December a4, mso. semi no. scuse.

Our invention relates broadly to heat treatment rocesses and more,particularly to a method of heat treatment of articles within anatmosphere of forcibly directed circulatory fluids. i i

One of theobjects of our invention 1s to provide a method of heattreating articles within an atmosphere of centrifu ally circulated gaseswithln a sealed retort or securing an improved qualit of product.

Another object o our invention is to provide a method of cracking andcirculating a process gas or fluid within a sealed retort and heatingthe same for subjecting varticles to a 'heat treatment process bycontact With the heated circulatory gases, which are mechanicallyagitated and directed within the retort.

We have found that articlesV treated according to theprocess of ourinvention have better quality and may be treated ina time eriodrelatively shorter than heretofore nown processes. Such heat treatingprocesses may consist of a method of changing the lsurfacecharacteristicsA of the material being processed, asin carbu'riz'ing andnitriding, or they may consist of a method for preventing changes in thesurface, as in bright annealing, or they may consist in the use ofreducing or inert gases for protection of the surface against oxidationlof the articles being heat treated.

In carrying out the process Vof our invention, We employ a furnace asset forth in Fred A. Hansens pending application, Serial No. 504,579filed December 24, 1930, in Whichany heat process may be carried out inany selected gas so circulated in a sealedl retort as to cause acomplete uniformityl of gas mixture and an unusually uniformdistribution of heat and of the application of the processing gas orfluids uniformly to all parts of the charge. y i

The process is not restricted solely to heat treatment of metal but mayalso be used in.A

thermochemical processes.

Our invention will be more fully understood by detailed reference to theaccompanying drawing which diagrammatically illusgally drivencirculatory system connectedI vwith the retort are readily impinged onthe heated face of the retort,v and are thereby cracked into two or morecomponent parts, and we have found further that in the circulatorysystem described in the said c0- pending application that thedissociated parts lof such gases have a directed flow, in

such a manner as to make available and more uniformly, to every particleof the charge, the

process effect required for most perfect production. In athermo-chemical reaction We may inject steam into the sealed retortWhere the charge in the container may he charcoal. 'lhe dissociatedcomponents of steam combine With the carbon atmosphere created b theheating of the charcoal and thereby form a hydro-carbon gas.Furthermore, by the introduction of steam and then heated to a certaintemperature, with the charge consisting of steel articles to be madeoxide or rustproof, We produce a more uniform result because the steamis iirst dissociated by the cracking effect hereinbefore described andthe circulation of the dissociated gases result in a more uniformdeposit of iron oxide as the protective coating. One or more catalyzersmay be inserted between the inner faces of the retort and the containerholding the articles to be processed. We are therefore able to modifythe gas mixture by means of the catalyzer in the circulatory system.

In the carburizing process, when using a hydro-carbon gas of correctquality, We have the carburizing method go through the same crackingprocess before contact with the charge as hereinbefore outlined. In asimilar manner, we more uniformly, and in a shorter time, successfullyperformv the bright annealing of non-ferrous metal such as co er bymeans of a steam atmosphere; t e

6 right annealin of steel in the container` by the injection of ydrogenor inert ases into the circulatory system, or we per orm such operationsas the tempering or drawing .of steel to a better uniformity mthoutspeclal 10 regard' to the control of atmosphere.

Our invention is applicable to Aman different processes, some of whichwe brie y describe as follows: v

N hiding-Subj ecting metallic substances, I6 such as-steel, malleableiron, Stellite, etc.,

to ammonia gases at approximately 950 F., Ato harden the surface and anyrequired depth below the surface.

Bower-Bar# procesa-subjecting steel to tEl) a steam atmosphere underpressure at approximately 1450 F. to impart a rust-proof nish.

arburz'zz'ng.-The process of subjecting comparatively low carbon steelto temperatures of 1650 to 1725 F. in a carbon gas atmosphere to imparta high carboncase thereon. In this process any carburizing compounds,such as hydrocarbon oils or hydrocarbon gases, bone ash, charcoal, coal,etc., may be used as a carburizing agent or carburizer. Bone ash,charcoal, coal, etc., are usuall used in a powdered or granular form.

rocessz'ng.-In these processes, steam, gases or liquids (such ascompounds of hydrocarbon oil) may be referred to as processing iiuids.

Annealng non-ferrous meterla- Copper in a steam atmosphere will annealat temperatures from 600 to 1200 F. according to the time cycle at suchtem eratures.

Annealz'ng or nomalzzz'ng steel.-This can be done by a. bright finishingprocess by introducing an inert gas inthe retort.

`Drawing and tempering sterf -Temperatures-vary from 400 to 1200 F.approximately. At above 950 F. the atmosphere may be hydrogen to preventscaling.

Referring to the drawing in detail, reference character 1 desi ates thefurnace casing which is lined with heat insulation material 2 providinga furnace chamber which is lined interiorly with electric heatingelements indicated at 3. While the chamber is shown heated electricallyit may be understood that the furnace can be heated b fuel and beeffective in the processes describe The electric heating elementsemployed along the interior walls of the furnace chamber are of theconstruction shown more clearly in Letters Patent No. 1,768,865 to EdwinL. Smalley, dated July 1, 1930. The upper portion of the casing isclosed by a top plate 4 in combination with a retort 9, the top plate 4having a trough 5 therein into which the downwardly extending flange 6of the rim plate 7 extends for establishing a seal for chamber 10 bymeans of sand indicated at 8. The rim plate 7 is sealed, as by weldingto the upper extremity of the retort 9 indicated at 9a, the retort 9depending downwardly into the furnace chamber' 10. A container 11 ismounted within the retort 9 and `is spaced from the interior wallsthereof by means of lugs 13 to allow the free circulation of stherearound. The container 11 is e evated from the bottom of the retort9 by suitable brackets shown at 12. The container 11 isapertured aroundthe side walls thereof and in the bottom thereof as indicated at 14. Thecontainer 11 encloses the charge indicated at 15. A top deflector 16 ismounted upon the container 11, the closure being frusto-conical in shapeand being centrally apertured as designated at 17.

The retorty is closed by a heat insulated cover member indicated at 18.The cover member projects downwardly into the retort and has a laterallyprojecting flange 19 which is secured to rim plate 7 by means 'of boltmembers 19a. A gasket 20 provides a gas tight seal between the covermember 18 and the rim plate 7 so that the retort is thereby sealed. Thecover member 18 is lilled with heat insulation material indicated at18a. A tripod support consisting of .frame members 21 is mounted on thecover member 18 and carries the driving motor 22. The rotatableg shaft.23 extends from motor 22 and projects through cover member 18 into theretort 9. A fan 24 is carried b the end of the shaft within the retortan serves to centrifugally circulate gases within the retort. A fan 25carried by shaft 23 is located'outside of the retort 9 and above thecover member 18 and serves to establish a forced draft for cooling themotor and shaft 23. That the shaft 23 is maintained in a lubricatedcondition during a carburizing process, may be understood by observingthe arrangement of the journal 26 in the cover member 18 having stufiingbox 27 in the upper portion thereof. The packing 28 is continuouslysaturated by the deposit of carbon particles liberated in thecarburizing process which particles are forced upwardly along a shaft 23into the packing 28. The shaft is not only thereby lubricated butleakage which might otherwise result is prevented by the cumulativecollection of carbon deposits in the acking.

WS provide inlet and outlet pipes represented at and 31 respectively,the pipes projecting through the cover member 18 constituting the top ofthe retort, horizontally beyond the perimeter of the fan 24 and providemeans for introducing hydro-carbon oils, hydrocarbon gases, or anyprocessing fluid, into the retort and into the circulatory system duringthe heat treatment process for establishing the required gas mixture andalso for introducing oil or other fiuids during the cooling cyclesubsequent to the heat treatment cyc e. Pipe 31 serves as a dlschargepipe for exhausting the retort. It is to. e noted that the introductionof any processing fluid at room temperature intoa highly heatedtemperature results in expansion of the resulting gases, and thattherefore b changing Athe amount of opening throug the valvecontrollingthe exhaust, all gases and pressure may be retained in theretort. In order to determine the temperature within the retort, weprovide a pipe 3 2 with closed bottom into which a thermo-couple may bepositioned. y

Between the inner wall of retort 9 and the container, 11 we may provideone or more catal zers indicated at 35 in the ath of the circu atorygases. We are there ore able to modify the gas mixture by means of thecatalyzer in the circulatory system. The processing fluids arepreferably injected into the discharge of the centrifugal fan, causingatomization and subsequently a forced impact against the side of retort9, which being heated readily cracks the processing fiuid into two ormore component parts into gaseous" form. Such gases being in thedirected flow from the centrifugal force are immediately available forintimate contact with every part of the charge, thus insuring a uniformtreatment by the combination of heat and the processing fluid.

Processing fluids may be injected on to the fan, on retort, orcontalner, and subsequently cracked and circulated, but not with themost satisfactory results obtained by the above described procedure.` Acentrifugal circulation of gases thus created is thereby directed incontact with the catalyyzers and through the perforated side walls andVperforated bottom of the container for the gas treatment of the heatedcharge within the retort.

After the charge has been heat treated for the required time period theretort is removed from the furnace chamber while maintaining the sealbetween the cover member 18 and the retort 9, and maintaining forcedcirculation in the retort, if desired. In a carburizing process usinghydro-carbon oil, we find it of value to continue the dripping of oil invery small quantities during the cooling process. The oil thus inducedand expanded into gases obviates the necessity of letting in air toprevent the collapse of the retort by vacuum resulting from suddenchilling. And if air were allowed during the cooling process it wouldresult in an oxidation of the charge. Furthermore, the oil induced inthe cooling cycle continues to be a carburizing means down to about 1400F. We have discovered, too, that the case produced in such a process,instead of having a marked line of demarkation between the case and thecore, gradually changes to the core condition without having reduced thedepth or eectiveness of the case, thereby improvin the quality byreducing the otherwise ten ency to brittleness.

Fig. 2 shows the retort with cover and driving motor thereon detachedfrom the fur-l nace, as when utilized for rapid cooling. Reardless ofthe fact that the retort has been etached from the heat treatmentchamber, the circulatory s stem may continue to operate thereby enab inthe charge to be cooled under uniform con itions producing a uniformproduct of high quality, as a uniform cooling produces a gram structurecommon to the entire charge.

We have found the heat processing in circulatory gases of our inventionto be highly practical and while we have described the pocess of ourinvention in its preferred emdiment, we desire that it be understoodthat modifications ma be made and that no limitations upon our lnventionare intended other than are imposed-bythe scope of the appended claims.Y

What we claim as new and desire to secure by Letters Patent of theUnited States is as follows:

1. In a heat treatment system includin a furnace having a sealed retortinsertale therein with means extending through and rotatively sealed ina cover for the retort and into the retort. for centrifugallydistributing the atmosphere in said retort, the method of sealing thepassage between the centrifugal drive means and the retort cover whichconsists in liberating carbon during a heat treatment process andforcing the carbon thus liberated into the seal between the centrifugaldrive means and the retort cover.

2. In a heat treatment system including a furnace having a sealed retortinsertable therein and a shaft extending thiough the cover for theretort and having a centrifugal fan thereon for establishing acentrifugal circulation of fluids within the retort, the methodoflubricating the shaft which consists in liberating carbon lwithin theretort and forcibly ejecting the carbon along the shaft and into thesealing means between the shaft and the cover.

3. In a heat treatment system including a furnace having a sealed retortinsertable therein with means extending through and rotatively sealedina cover for the retort and into the retort for forcefully distributingthe atmosphere in said retort, the method of sealing the passage betweenthe centrifugal drive means and the retort cover which consists inliberating carbon during a heat treatment process and forcing the carbonthus liberated into the seal between the drive means and the retortcover.

4. In a heat treatment system includin a furnace having a sealed retortinsertale therein and a shaft 4extending through the cover for theretort and having a fan thereon for establishing a, forced ircultion ofuids the retort, the method of lubrieating the shaft which consists inliberating l' carbon within the retort and forcibly eject- -5 ing thecarbon along the shaft and into the sealing means between the shaft andthe COVel.

tures.

HAROLD E. KOCH. MEINILLE LQWE.

In testimony whereof we aix our signai'

